Heavy alcohol consumption is associated with significantly increased risk for atrial fibrillation, at least among men, according to an article in the September 13 issue of Circulation.

Kenneth J. Mukamal, MD, lead author of the study, said “There has been disagreement about the risk of moderate drinking with regard to atrial fibrillation. Some studies have suggested the risk mainly appears to be in heavy drinkers. In other studies, researchers have seen an increased risk with what most people would consider moderate drinking, on the order of 1-2 drinks a day.

The advantages of our study were that we had more than 1,000 cases of atrial fibrillation and we had a much broader range of drinking habits compared to other studies. That gave us a chance to home in on individual drinking levels to an extent that other studies have not been able to do.”

In the current study, researchers evaluated 16,415 adults (7,588 men, 8,827 women; average age, 50 years) in the Copenhagen City Heart Study. On three occasions, participants had a routine electrocardiogram and completed a questionnaire regarding medical history, socioeconomic status, and exercise, smoking, and drinking habits.

People with atrial fibrillation at study outset were excluded from analysis. Other exclusion criteria were history of coronary heart disease or stroke and use of heart or antihypertensive medications.

Most subjects enrolled at the first time point, 1976-1978, and were followed to the end of the third time point, 1991-1994. Over time, participants reported intake of beer, wine, and spirits. Response categories were “never/hardly ever,” “monthly,” “weekly,” and “daily.” Daily drinkers reported number of drinks per day.

For purposes of analysis, researchers used the following categories of drinks consumed weekly: less than 1, 1-6, 7-13, 14-20, 21-27, 28-34, and 35 or more. Women included fewer heavy drinkers, so their top range was 21 or more drinks per week.

Men were more likely to report either 1-6 drinks (1,703, 22.4 percent) or 7-13 (1,799, 23.7 percent) per week. Roughly 12.5 percent of men were in the top category of more than 35 drinks per week--- mostly beer.

Almost half of women reported 1-6 drinks, and only 3.5 percent (315) reported they were in the top category of 21 or more drinks.

Researchers documented 1,071 cases of atrial fibrillation during follow-up. Risk for atrial fibrillation was similar between abstainers and people who drank up to 14 drinks weekly. In men, risk was slightly higher up to 34 drinks per week. However, risk increased by 45 percent in men who had 35 or more drinks weekly compared to those who hardly ever drank.

After adjustment for factors including blood pressure, coronary heart disease, and heart failure, risk increased by 63 percent for men in the highest consumption category compared with those in the lowest category. Results were not affected by age or body mass index.

Similar analysis for women did not find a comparable increase in risk for women in the top consumption category, perhaps because the top category was so much lower than for men. Mukamal noted that although the results apply primarily to men, it is reasonable to conclude they apply to women, too.